1. Field Of The Invention
The present invention relates broadly to the field of a coupling assembly, and more particularly to the field of a threaded coupling assembly for use in forming a tubular conduit string used in wells.
2. Background Art
Coupling assemblies for structurally or operably joining or connecting separate items or components to form useful machines and articles of manufacture are well known in many applications. One such known application is in handling fluids (gases, vapors, liquids or combinations thereof including entrained or suspended solid matter) by operably connecting or joining lengths of tubular conduits, tubes or pipes to form a pipe spool, flow line or fluid handling system providing a desired, contained, continuous, internal fluid flow passage or path between two spaced locations. An essential requirement of a coupling assembly in many flow line applications is the capability to repeatedly and quickly assemble or disassemble the pipe or tubes into the connected desired flow system. Pipe coupling assemblies usually, but not always, employ some form of a helical thread or screw arrangement for joining, securing or connecting the pipe ends in flow communication. This threaded construction also enables the pipe coupling to be repeatedly reused rather than being replaced each time the pipes are connected for forming the fluid handling system. Such pipe couplings also normally include means for sealing the connected pipe sections to contain or prevent escape or leakage of fluid from or into the internal flow passage of the pipe between the two locations. Some examples of releasable and reusable coupling assemblies used for pipe connection purposes include the following U.S. patents:
______________________________________ U.S. Pat. No. Patentee Class/Subclass ______________________________________ 2,635,900 Mayo 285/59 3,163,448 Franklin 285/137 3,680,188 Mason et. al. 29/157 3,686,747 Bagnulo 29/5508 4,621,841 Wakefield 285/158 4,695,080 Oetiker 285/334 ______________________________________
See also British patent document no. 1,174,208 to Benter-Werke Aktiengesellschaft.
Wells bored, drilled or otherwise formed into the earth's crust for a wide variety of useful purposes involving fluid handling are also known. In drilling or boring such wells it is common practice to provide a circulation system for drilling fluids. In the recovery of hydrocarbons, minerals and other forms of energy such as geothermal, it has been useful to form wells that penetrate into the earth's crust to obtain access to the desired subsurface target or formation. Some wells are used for disposal or injection of waste, usually hazardous, into a subsurface earth formation. Other wells are used for temporary storage of hydrocarbons. Tubular well strings or conduits formed by connecting lengths of metal pipe or tubular conduits with coupling assemblies are widely used for many purposes in the well environment and in all phases or stages including drilling, casing, flowing and maintaining a well. By connecting the ends of the lengths of the pipe in an end to end or series flow communicating relationship with the coupling assemblies a well string of any practical desired length may be formed. The various applications, use or purposes of well strings create unique requirements for the coupling assemblies used to join the pipes or tubes.
Such tubular well strings formed by the use of coupling assemblies have acquired various labels, names and meanings in the industry that while commonly used are not always precise and altogether free of confusion. For example, a well casing string is often arbitrarily distinguished by some from workover strings, production tubing, well liners or drilling strings by the various sizes and dimensions of the pipe as well as the intended purpose or use of the string in the well. As used herein the terms "well string" or "well conduit" shall be interchangeably defined to cover all sizes and all applications or of uses of operably connected tubular conduits, tubes or pipes in the well environment. There has also been definition confusion over the term or word "joint" in well applications. In one context that term has been used to designate the connection of the pipe ends (pipe joint) while in another context has been used to identify a certain length of pipe(pipe joint or joint of pipe). As employed herein the term "joint" will be used to describe or define a length of pipe.
For a number of reasons, including adequate strength and the capability of repeated make up or assembly, the preferred manner of coaxially connecting or securing the individual lengths of pipe with the coupling assembly to form the desired well string employs interengaged helical threads. The mating member having the external thread structure is commonly referred to as the pin while the member having the internal thread structure is frequently identified as the box. The interengaged thread structure may be formed or manufactured on a constant diameter (cylindrical) or on a taper (conical) relative to the longitudinal axis of the coupling or tube. By controlling the axial or longitudinal length of the thread engagement, a suitable area of thread engagement can be provided for carrying the anticipated load. In many well strings the engaged threads are not strained to plastic deformation when rotational made up for enabling the highly desirable repeated coupling use. The most common or widely used coupling assembly in well applications utilizes metal pipes or tubes having external helical pin threads that engage mating internal box threads formed in the longitudinal bore of a metal coupling member, sleeve or collar. This type of coupling assembly is often referred to a threaded and coupled (or simply T&C) to distinguish from other forms of pipe couplings used in forming well strings or conduits. Normally, but not always, the coupling assembly for well strings also provides a fluid seal between the connected pipes. Seals for the coupling assembly to prevent leakage of fluid may be formed by metal-to-metal contact or some form of gasket depending on coupling geometry and intended application. Various well pipe coupling assemblies thread profiles, seals and their arrangement or geometry as well as their materials of construction are commonly known and some have become industry (American Petroleum Institute or API) standards. Coupling assemblies for forming well strings are commercially available from a large number of manufacturers, including the assignee of the present invention, that conform to either API and proprietary specifications.
While many well strings are exposed to, conduct or otherwise contact fluids that are not damaging to metals others are exposed to well fluids are highly corrosive to many metals. When such corrosive fluids are encountered or anticipated to be present in a particular well, special precautions must usually be taken to protect the well string from failure induced or accelerated by corrosive attack. Special corrosive resistant alloy materials of construction may be used in some instances to form the well conduit components exposed to the corrosive fluids, but that approach is usually undesirable due to the much greater cost of the alloy materials. In addition, corrosion resistant metal alloy materials often lack adequate strength qualities to carry the loading forces or safely withstand the localized high stress and strain loading created by the interengaged threads or metal-to-metal seals in these applications. Lined well conduits have also been employed to solve this corrosion problem as their cost is often not as great and they retain the strength quality and elastic strain capability of alloy steel. Both internal metal and plastic linings have been employed as protective corrosion barriers to isolate or shield the metal tubes and couplings of these well conduits from exposure to contact with the corrosive fluids present or flowing through the interior flow passage or bore of the well conduits. While such lined construction has been generally successful in protecting the well conduit there have been problems and failures. Generally such protective barrier failures occur in the vicinity of the pipe ends and coupling assembly as a result of fluid leakage due to failure of the corrosion barrier seal employed. Such corrosion barrier seal failure may result from any one of a multitude of factors. Due to the high level of tensile stress resulting from the combined force loadings, the seal and threaded areas of the pipe or coupling are particularly vulnerable to corrosive attack when a corrosion barrier seal fails. The long felt need for a dependable, rugged corrosion barrier seal for a tube or pipe coupling assembly that can be reliably assembled to form a string in the hostile environment at a well site has been widely recognized.
Examples of prior art patents for well string coupling assembly applications include the following:
______________________________________ U.S. Pat. No. Patentee Class/Subclass ______________________________________ 2,261,566 Russell et. al. 285/371 2,487,241 Hilton 285/334.2 3,266,821 Safford 285/55 4,507,842 Werner 285/371 3,572,777 Blose 285/334 4,679,831 Kielmanski 285/332.2 4,568,113 Axford et. al. 285/334 4,655,485 Albrecht et. al. 285/333 4,706,997 Carstensen 285/13 4,711,474 Patrick 285/332.3 4,856,828 Kessler et. al. 285/334.1 3,100,656 MacArthur 285/55 4,830,411 Tsuru et. al. 285/334 ______________________________________
As disclosed in expired Russell U.S. Pat. No. 2,261,566, it is known to use threaded tubular coupling assemblies having a coupling member formed with internal threads for coaxially connecting lengths of tubes or pipes having external threads and an internal corrosion resistent coating of organic resin or the like for forming a tubular well string or conduit is known. To protect the highly stressed threaded area of the pipe and coupling member from the corrosive fluids, Russell employs as a corrosion barrier a metal fitting or sleeve having a corrosion resistent coating for sealing with the mated pipe ends and which extends into the bore of the tubes. No annular stop or torque shoulders are provided by the Russell coupling assembly for limiting rotational make up of the pipe external threads to position the pipe ends in a predetermined relationship to the metal fitting or coupling. If the threads are inadvertently rotationally made up for too great a longitudinal distance or length into the coupling member, the corrosion barrier fitting may be displaced from the proper sealing position at the pipe ends or even destroyed therebetween by crushing.
The Hilton patent U.S. Pat. No. 2,487,241 discloses a pipe coupling assembly in which a resilient corrosion resistant annular gasket is trapped between and fills the otherwise open annular gap within the coupling between the opposed pipe ends to provide a corrosion barrier seal and a continuous smooth interior surface to flow. The smooth interior flow passage between the tubes is desirable as it protects the pipe and coupling from damage by eliminating turbulent, erosive flow resulting from the gap between the connected pipe. To withstand crushing by the tube ends and displacement from the sealing location by a greater pressure external to the coupling, the resilient gasket must be reinforced to maintain its desired sealing capability. No torque or stop shoulders are provided on the coupling assembly for limiting thread make up and positioning of the pipe ends in the coupling member to prevent such crushing or inadvertent forcing or displacement of the gasket by the pipe ends from the sealing location.
In U.S. Pat. No. 3,266,821 to Safford a sealed pipe coupling is disclosed for use in corrosive and erosive well fluid service. The coupling sleeve threadedly engages the tapered threaded pipe in the usual manner, but the engaged thread area and resulting physical strength of the coupling is reduced by this arrangement. An annular recess is provided in the inner wall of the coupling between the longitudinally spaced threaded portion for receiving a plastic gasket. The plastic gasket is shaped to grip the external pipe threads during make up to prevent displacement. No torque shoulder engagement for limiting thread make up or effecting a metal-to-metal seal is provided.
Werner U.S. Pat. No. 4,507,842 also discloses a system for connecting plastic lined pipe joints using a tubular corrosion barrier liner sleeve that concentrically fits in the bores of the pipes. The liner sleeve is placed in the bore of the pipe coupling or collar during thread assembly of the connection and seals with the inside diameters of the pipe bores by a pair of longitudinally spaced O-rings. The linear sleeve forms an outwardly extending collar that is trapped in the coupling between the opposed pipe noses to maintain the desired positional relationship for sealing. The restricted internal open area of this liner construction is undesirable both for limiting internal flow capacity and preventing use of through the bore or flow line movable well tools.
In Blose U.S. Pat. No. 3,572,777, the use of an annular resilient gasket between the pipe ends and within the coupling in place of the an inwardly projecting integral collar on the coupling sleeve is disclosed for use in severe and corrosive well fluid service. The plastic gasket, due to a flange and shoulder construction arrangement, is T-shaped in cross-section prior to make up. An internal groove is machined in the coupling sleeve to a longitudinal dimension to accommodate the flanges rather than the gasket shoulders. If the threads are correctly made up the undercut portions of the pipe ends trap the flanges against the coupling to prevent the gasket from being squeezed out. If the thin flanges are partially displaced from the groove during rotational make up of the threads, sealing integrity is lost. The secondary metal-to-metal seal is formed by engagement of shoulders formed on the pin and outer annular end shoulders of the coupling which also limits thread make up to prevent displacement of the plastic gasket.
U.S. Pat. No. 4,679,831 to Kielmanski discloses a pipe coupling assembly having a corrosion barrier formed by a floating metal ring substantially encased in a suitable resilient plastic jacketing or coating material. The floating ring eliminates turbulence corrosion at the coupling while enabling passage through the bore of movable hardware items, such as through the bore transportable well tools. Two longitudinally spaced grooves are formed in the coupling to provide the movement limit stops for the floating sealing ring. A tapered thread arrangement is employed which by torque build up limits thread make up. Due to the variable thread friction, such arrangement does not result in an assured precise positional relationship between the coupling and pipe for requiring the seal to float axially or longitudinally relative to the coupling. And even then the plastic coating may be crushed to destruction.
Axford U.S. Pat. No. 4,568,113 discloses the use of a generally tubular metal washer or ring carried within the coupling between the stainless line steel (bimetallic) pipe members to provide a continuous internal metallurgical corrosion barrier or primary seal when used in H.sub.2 S or CO.sub.2 service. The washer forms metal-to-metal seals with the stainless steel liner and is preferably made of the same stainless or other corrosion resistent material. Each of the engageable threaded surfaces has both a cylindrical and tapered portion.
The patent to Albrecht et. al. (4,655,485) discloses a deformable plastic ring for sealing in the engaged thread area rather than the pipe ends. One of the engaged thread surfaces is formed with a recess into which the plastic rings are placed. Upon thread make up the plastic is deformed sufficiently to provide the desired seal in the engaged thread area.
U.S. Pat. No. 4,706,997 to Carstensen discloses a coupling assembly having a separate floating internal precision makeup ring which serves as a makeup stop shoulder to control the tube positioning distance relative to the other tube upon make up, but does not consistently position the tube ends relative to the coupling member. A plastic seal ring is concentrically mounted between the separate tube end positioning ring and the outer coupling member to form the corrosion barrier. In other embodiments the integral internal ring or collar on the coupling maintains or traps a pair of plastic seal rings in position for sealing with exterior conical surfaces on the tubes but does not form a protective corrosion barrier for the coupling.
U.S. Pat. No. 4,711,474 to Patrick discloses use of a plastic seal ring located within the threaded area of a pipe coupling which precludes its use as a corrosion barrier. The plastic seal ring is carried in a groove in the threaded area on one member and sealingly engages with the threads on the mating member after make up.
Kessler U.S. Pat. No. 4,856,828 discloses the use of an annular rigid plastic liner sealing gasket for interior plastic coated pipe or tubes. The gasket forms a pair of flanges which extend into the pipe bore to seal with the cylindrical interior marginal surface of the tubing as well as effecting a separate seal of the center radial portion of the gasket with the pipe ends. Not only does such liner gasket construction create a downstream flow turbulence, it also blocks passage of well tools. No stop means for controlling thread make up to prevent crushing or forcing or displacement of the plastic gasket into the pipe bore are provided.
The MacArthur patent (3,100,656) discloses the use of a plastic corrosion ring barrier for sealing lined pipe in an integral tubular coupling. Integral threaded pipe coupling connections usually employ expensive, wall thickening upsets on the tubes to provide the necessary strength or structural integrity normally provided by the separate coupling sleeve member. The thickened portion of the box or internally threaded pipe member is provided with a single sided recess for receiving the plastic ring that is generally sealingly deformed to a "dumb bell" or I-shaped cross section configuration when fully compressively engaged by the pin nose upon thread make up. The plastic seal ring is slightly over-size in outer diameter in relationship to the outer wall diameter to provide an initial pre-compressed condition to control "writhing" during the relative rotation movement necessary to effect thread assembly. The seal ring, which is initially substantially square in cross section, has an inner diameter substantially equal to the bore diameter of the pipe for leaving an internal uninterrupted passage therethrough for movement of various well tools. As the plastic ring seals with the internal corrosion resistant lining of the tubes, the threads and annular make up shoulders are protected from undesired contact with the corrosive fluid.
U.S. Pat. No. 4,830,411, to Tsuru et. al., which is assigned to the assignee of the present invention, discloses a reusable threaded coupling for oil-well pipe service. The disclosed coupling forms a metal-to-metal annular seal and torque stop shoulder between the tubes and coupling member. The metal coupling member is exposed to the well fluids although a continuous smooth internal flow path is provided.
Each of the above indentified patents are hereby fully and completely incorporated in the written description of the present invention by this specific reference as if each so identified patent had been set forth verbatim herein.